Autoamtic truing mechanism



May 24, 1960 G. L. GROVE AUTOMATIC "mums MECHANISM 4 Sheets-Sheet 1Filed Aug. 5, 1957 INVENTOR. GEORGE L. GROVE BY ZWWIM ATTORNEYS May 24,1960 5. L. GROVE AUTOMATIC TRUINC MECHANISM 4 Sheets-Sheet 2 Filed Aug.5, 1957 INVENTOR. GEORGE L. GROVE May 24, 1960 c. GROVE AUTOMATIC TRUINGMECHANISM 4 Sheets-Sheet 3 Filed Aug. 5, 1957 IN VEN TOR.

GEORGE L. GROVE WWW AZ /%Z 99 93 QZJ Z YWMW ATTORNEYS United StatesPatent 1O AUTOMATIC TRUING NIECHANISM George L. Grove, Cincinnati, Ohio,assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, :1corporation of Ohio Filed Aug. 5, 1957, Ser. No. 676,195

7 Claims. (Cl. 125-11) 2,937,639 Patented May 24,

ICC

Fig. 5 is a cross-sectional view taken along the line- 5-5 in Fig. 3.Fig. 6 is a cross-sectional view taken along the line 6-6 in Fig. 3. V v

Fig. 7 is a wiring diagram showing the electrical control circuits forthe automatic truing mechanism.

In the detailed specification to follow, similar refer ence charactersdesignate similar or identical elements and portions throughout thespecification and throughout the different views of the drawings.

In Fig. 1 is shown a centerless grinding machine of known constructionto which there is shown applied the automatic truing mechanism formingthe subject matter of the present invention. It is to be realized,however, that the automatic truing mechanism may equally well be appliedto other known forms of grinders of either centerless or center typeconstruction. As shown in Fig.-

1, the grinder is provided with abase 10 upon which is supported a pairof spaced grinding wheels 11 and 12 (see Fig. 6) enclosed within a guard13. The grinding the amount of advance of the diamond on each pass andthe number of passes thereof being predetermined by the operator so thatupon depression of a push button a completely automatic truing cycle canbe'eifected. Thus, uniform truing of the wheel is insured, togetherwheels are suitably journaled in bearings supported on the base 10 andare driven by a motor (not shown) also supported on the base. A pair ofcorrespondingly spaced regulating wheels 14 are supported on a carriage225 15 which is mounted for sliding movement on a lower.

with an attendant saving of time since the advance of v the diamond,turning on of the coolant for each pass, and reversal of the traversingcarriage at the end of each pass is' effected in a predeterminedsequence and without delay.

Accordingly, it is an object of the present invention to provide a fullyautomatic .truing cycle for grinding machines which enables a completetruing operation to be effected by a single depression of a push button.

Another object of the invention is to provide an automatic truingmechanism in which the amount of advance of the diamond on each pass andthe number of truing passes etfected by the diamond may be set into themechanism in advance and thereby determine the character of allsubsequent truing cycles.

Another object of the invention is to provide an automatic truingmechanism in which the setting of the reversal points of the traversingcarriage on which the diamond is mounted also determines the .pointsatwhich coolant flow to the wheel will be initiated, thereby simplifyingthe set-up of the machine for a particular job.

Another object of the invention is to provide an automatic truingmechanism which is adaptable to the truing of a plurality of spacedgrinding wheels by a single diamond, the latter being moved in rapidtraverse from one slide 16 which carries a work rest blade 17 forsupporting the workpiece 18. Suitable driving means is provided forrotating the regulating wheels and a power feed mechanism is customarilyprovided for moving the carirage and regulating wheels toward theworkpiece to effect a grinding operation and to withdraw the wheelstherefrom after the operation has been completed.

After a predetermined number of workpieces have been ground by themachine, it is necessary to truethe grinding wheels and, for thispurpose, a diamond truing mechanism 20 has been provided. This mechanismis supported on a bracket 21 mounted on the base of the machine as shownin Fig. 1. In accordance with the present invention, the truingoperation is rendered fully automatic, the operator merely selecting thenumber of truing passes to be made by the diamond by appropriate settingof a dial 22 on a counter 23 contained in an electrical cabinet 24. ATruing Start push button 19 is then depressed to cause the diamond totraverse back and forth across the wheels 11 and 12 with automaticadvance of the diamond to remove the necessary amountof material fromthe wheels on each pass and thereby provide an accurate and sharpsurface thereon. The means whereby this is accomplished will bedescribed in detail in the succeeding portions of the specification.

wheel to the next so as to shorten the truing cycle to the fullestpossible extent with this type of truing mechamsm.

With these and other objects in view, which will become apparent fromthe following description, the invention includes certain novel featuresof construction and combination of parts, the essential elements ofwhich are set forth in the appended claims and a preferred form orembodiment of which will hereinafter be described with reference to thedrawings which accompany and form a part of this specification.

In the drawings:

Fig. 1 is a side elevation of a centerless type grinding machine towhich the invention is shown applied.

Fig. 2 is a diagrammatic view of the hydraulic circuit of the machineshown in Fig. 1. p

Fig. 3 is a cross sectional elevation of the truing mechanism shown inFig. 1.

Fig. 4 is a view showing a development of the diamond advance selectorbushing shown in Fig. 5.

As shown in Fig. 3, there is secured to the upper surface of the bracket21 a bed plate 28 which is provided with a dovetail rib 29 whichcooperates with correspondingly shaped ways provided in the bottom of acarriage 30 which is provided with a flat bearing surface 31 adapted toseat upon a corresponding surface provided on the bed plate 28. Thecarriage will thereby be guided for rectilinear sliding movement on thebed plate 28. 1 Supported within the carriage 30 for sliding move-' mentin a direction perpendicular to that of the carriage is a slide 35 whichis bored in a longitudinal direction to receive a diamond truing bar 36.The slide is sup ported for translation in the carriage 30 by means of apair of longitudinally extending grooves disposed on either side of theslide as shown in Fig. 6 in which are seated balls 37 which are receivedin grooves in rails 38 suitably secured within the carriage. The slide35 is therefore free to move in its longitudinal direction within thecarriage, the balls 37 running freely in the grooves provided thereforin the slide and in the rails 38 so as .to provide an anti-frictionbearing for the slide. The

diamond truing bar 36, which is of hollow tubular con struction, issupported for sliding movement within the slide 35 by means of bearingsurfaces 40 and 41 pro vided at the ends of the slide. As viewed in Fig.3, the bar 36 is secured at its left hand end to a bracket 44 which, inturn, is attached to a housing 45 which contains the diamond advancingmechanism- At its right hand end the truing bar 36 carries a diamondturner 46 of known construction which supports the truing diamond 47inposition to engage the periphery of the grinding wheels 11 and 12. Thewheel guard 13 is provided with an elongated opening 48 foraccommodating the truing bar and permitting it to travel back and forthacross the wheels. 7

The advance of the diamond toward the wheels prior to each truing passis effected by means of a feed screw 50 which is rotatably journaled atits left hand end in the housing 45 and is held against axial movementwith respect thereto by a flange 51 formed on the lead screw and a hub52 provided on a hand wheel 53 secured to the left hand end of the leadscrew. At its right hand end, the lead screw 50 threads into a collar 54secured to the left hand end of the slide 35 whereby rotation of thelead screw will feed the truing bar 36 relative to the slide 35.

The position of the slide 35 with respect to the carriage 30 isdetermined by a profile cam 56, suitably secured to the bed plate 28,and a cooperating cam follower 57 fastened to the collar 54. The camfollower is maintained in contact with the profile cam 56 by means ofsprings (not shown) which act on the slide 35 and urge it to the rightas viewed in Fig. 3. The action of the springs on the slide may bemodified by manual pressure applied to a hand lever 58 secured to a stubshaft 59 journaled in the carriage 30. The shaft 59 carries aneccentrically mounted pin 60 which engages in a cross clot provided inthe top of the slide 35 to provide control thereof by the hand lever.

Traversing movement of the carriage 30 on the bed plate 28 is effectedby means of a lead screw 63 supported at its ends in the plate 28 andmeshing with a nut 64 mounted in the carriage 30. The lead screw isdriven by a hydraulic motor which will be described in connection withthe hydraulic diagram in a later portion of this specification.

As shown in Figs. 3 and 6, the carriage has mounted on its forward endan elongated bar 66 on the opposite ends of which are mounted dogs 67and 68 which are adjustable along the length of the bar and which may beclamped in adjusted position by means of bolts 69, the heads of whichare received in a T slot 70 (Fig. 3) provided in the bar 66. The dog 67is adapted to cooperate with the contact roll 71 of a limit switch 2LSwhile the dog 68 is adapted to cooperate with the roll 72 of a limitswitch 3L5. These limit switches, together with a third limit switch LS,are supported in a housing 75 carried by the wheel guard 13.Intermediate the dogs 67 and 68 there is secured to the bar a rapidtraverse cam 73 which is adapted to cooperate with the contact roll 74of the limit switch SLS.

Advance of the diamond truing bar 36 may be effected either manually bymeans of the hand wheel 53 or automatically by means of a pawl andratchet mechanism driven by a feed piston 80. As shown in Figs. 3 and 5,the piston 80 is slidably received within a cylinder 81 provided in thelower portion of the housing 45. As shown in Fig. 5, the right hand endof the cylinder is closed by a cap 82 suitably secured to the housing,while the left hand end of the cylinder is closed by a bushing 83 whichis adjustably secured to the housing 45 by cap screws 84 and set screws85. The bushing 83 is provided with an axial bore for receiving the stem86 of a diamond advance selector knob 87 which may be turned to any oneof four positions to provide different amounts of diamond advance. Asshown in Fig. 5, the right hand end of the stem 86 serves as a stop tolimit left hand movement of the piston while the cap 82 serves as a stopto limit right hand movement of the piston within the cylinder. Thepiston is bored to receive a compression spring 88 which presses on thestem 86 and thereby urges a pin 89 projecting radially from the sterninto engagement with the inner edge of the bushing 83.

As more clearly indicated in Fig. 4, the edge of the bushing 83 isprovided with four notches 90 of varying depth for receiving the pin 89.Hence, by pressing in on the knob 87 and turning the same, any one ofthe notches 90 may be selected to receive the pin 89, thereby providingfour different degrees of adjustment of the inner end of the stem 86relative to the left hand end of piston 80. Thus, for diflferent strokesof movement are permitted the piston, which strokes are effected underhydraulic pressure controlled by a valve located in the bottom of thehousing 45. This valve includes a spool 93 (Fig. 5) which is slidable ina cylindrical bore provided in the base of the housing and which isurged toward the right by a compression spring 94. The spool is therebymaintained with its right hand end bearing against the inner edge of abushing 95 located in the end of the cylindrical bore. An intermediateportion of the bore is connected by a channel 96 with the right hand endof the cylinder 81. When the spool 93 is in the position shown in Fig.5, this channel is communicatively connected with an exhaust line 97,thereby permitting the spring 88 to move the piston 80 to the limit ofits movement in the right hand direction. However, when solenoid 6SOL isenergized, a plunger 98 passing through a bore in the bushing 95 will beprojected outwardly against the right hand end of the spool 93 and shiftthe latter to the left against the force of the spring 94. With thespool in this position, the channel 96 will be communicatively connectedwith a pressure line 99 whereby hydraulic fluid under pressure will beadmitted to the right hand end of the cylinder 81 thereby driving thepiston 80 to the left. When the solenoid is deenergized, the spring 94will return the spool to the position shown in Fig. 5 thereby againconnecting the right hand end of the cylinder 81 with the exhaust line97 whereupon the spring 88 will return the piston to the position shownin Fig. 5. As heretofore mentioned, the stroke of the piston isdetermined by the setting of the selector knob 87 so that differentdegrees of advance of the diamond may be obtained.

As herein shown, the upper edge of the piston 80 is provided with rackteeth which mesh with the teeth of a spur gear 100, the upper portion ofwhich is removed to provide a seat for a block 101 which is screwed fastto the gear. Situated adjacent the gear 100, which is freely rotatableon the feed screw 50, is a ratchet wheel 102 which is pinned to thescrew 50 as indicated'in Fig. 3. The wheel 102 is arranged to be drivenby a pawl 103, which is pivoted on a stud 104 carried by the block 101and is urged by acompression spring 105, interposed between the blockand the pawl, in a clockwise direction about the stud 104 to engage thepawl with the teeth of the ratchet wheel 102. Hence, when the piston 80is driven to the left as viewed in Fig. 5 thereby turning the gearclockwise, the pawl 103 will turn the ratchet Wheel 102 and the leadscrew 50 in a similar direction. When the piston 80 returns to theright, thereby driving the gear 100 in a counterclockwise direction, thepawl 103 will ratchet over the teeth of the wheel 102 and the feed screw50 will remain stationary. Depending on the setting of the selector knob87, the ratchet wheel will be advanced through a distance of one, two,three, or four teeth thereof and cause corresponding amounts of diamondadvance.

To permit manual operation of the feed screw 50 in either direction bythe handwheel 53, an Auto-Manual selector knob 108 is provided on theside of the housing 45. This knob is adapted to rotate a hub 109carrying an ecc'entrically mounted lug 110 which underlies the righthand end of the pawl 103. Hence, when the knob 108 is turned 180degrees, the lug 110 will elevate the pawl and disengage it from theteeth of the ratchet wheel 102. At the same time, the upper edge of thepawl will engage the plunger of a limit switch 4LS mounted on a bracketin the top of the housing 45 and, through means hereinafter to bedescribed, will thereby disable the automatic truing control circuit.

. As hereinbefore-stated, the diamond turner 46 (Fig. 3) is ofconventional design and is adapted to be operated by hydraulic fluidunder pressure admitted through a coupling 115 to the interior of a tube116 by which it is transmitted through the truing bar 36 to the diamondturner 46. The construction of the turner 46 is such that when pressureis admitted to the tube 116 the diamond 47 will be turned, and upon adrop of pressure within the tube 116, the diamond turning mechanism willbe reset ready for the next operation.

The hydraulic control circuit for the automatic truing mechanism isshown in Fig. 2 of the drawings. As therein indicated, fluid underpressure is delivered to the pressure line 99 by a hydraulic pump 120driven by an electric motor (not shown). The pump draws fluid out of asump or reservoir 121 for delivery to the pressure line 99in which thefluid is maintained under constant pres sure by a relief valve 122 whichdischarges excess fluid into the reservoir 121. The exhaust line 97returns fluid to the reservoir from the various hydraulic componentscontained in the circuit.

As heretofore mentioned, the feed screw 63 (Figs. 2 and 3), whichtraverses the carriage 30 back and forth with respect to the grindingwheels 11 and 12, is driven by a hydraulic motor which is indicated inFig. 2 by reference numeral 125. This motor is connected by hydrauliclines 126 and 127 to a reversing valve 128. This valve is controlled bya solenoid operated pilot valve 129 which valves fluid under pressure tothe ends of valve 128 through lines 130 and 131, thereby shifting thelatter valve in one direction or the other. The pilot valve 129 containsa spool 132 which is held in a centered position within the valve bodyby means of compression springs 133 and centralizing washers 134. Thevalve is provided with a centrally located pressure port which isconnected to the pressureline 99, and with a pair of exhaust portslocated on opposite sides of the pressure port which are connected withthe exhaust line 97 through a check valve 135 and suitable linesconnecting the ports with the check valve. Hence, when the solenoid 3SOLis energized, the spool 132 will be shifted to the left, as viewed inFig. 2 thereby connecting the line 130 with the pressure line 99, andthe line 131 with the exhaust line 97. This will cause pressure to beapplied to the left hand end of the reversing valve 128 and will connectthe right hand end of this valve with the exhaust line 97. As a result,a spool 138 which is normally held in acentered position by compressionsprings 139 and centralizing washers 140, will be shifted to the rightthereby opening pressure from a port 141 connected with pressure line 99to the motor line 127 and connecting motor line 126 with an exhaust port142 connected to areturn line 143. The motor 125 will thereby be rotatedin adirection to drive the carriage 30 away from home position, i.e.,the position in which dog 67 (Fig. 6) is in, contact with roll 71. g thesolenoid 4SOL is energized, the spool 132 will be shifted to the rightto cause spool 138 to be shifted to the left, thereby opening a pressureport 144 to the motor line 126 and connecting the return port 142 to themotor line 127. This will cause the motor 125 to rotate in the oppositedirection and move the carriage 30 from a reversal position, asrepresented by engagement of the dog 68 with the contact roll 72 (Fig.6), toward home positionfurther shown in Fig. 2, the return line 143 iscon- If, on the other hand,

nected by line 145 with a pressure reducing valveJ146; This valvecontains a sliding plunger 147 containing a transverse bore 148 andalongitudinal bore 149 cornmunicatively connected therewith. The bore149 extends to the bottom of the plunger 147 and transmits fluid to achamber 150 provided'in the bottom of the valve. The pressure of thefluid in the chamber 150 will tend to raise the plunger 147 against theurgency of a compression spring 151 acting downwardly on the top oftheplunger, this upward movement of the plunger tending to cut 011 theport to which line 145 is connected. Accordingly, the pressure willbe-stabilized when the pressure in the chamber 150 equals the pressureacting on the top of the plunger through spring 151 and fluid underconstant pressure admitted to the top of the valve through a line 152.Since the downward force acting on the plunger is constant, the pressurein chamber 150 will also remain constant, and a constant pressure willthereby be maintained at the outlet port 153. This port is connected bya line 154 with a rate valve 155 which may be adjusted by rotating aknob 156 to vary the amount of oil permitted to fiow throughan outletport 157 on the valve. This port is connected by a line 158 with arelief valve 159 which is connected by a line 160 with the exhaust line97. The pressure in the line 158 will thereby be maintained constant atthe setting of the relief valve 159 whereby the oil admitted throughline 152 to the top of the pressure reducing valve 146 also willbe'maintained constant. The pressure thereby provided on top of theplunger 147 will assist the spring 151 and provide more linear operationof the pressure reducing valve. Hence, by suitable adjustment of therate valve 155, through manipulation of knob 156, the feed rate of thediamond across the grinding wheels may be adjusted as desired.

To provide for rapid traverse of the diamond from one grinding wheel tothe next, a rapid traverse valve is provided for by-passing the ratevalve and con-' necting the return line 145 directly to the exhaust line97. This valve is provided with a spool 166 which is normally held inits left hand position as shown in Fig. 2 by compression spring 167. Inthis position of the spool, a line 168 connected to the return line 143is blocked by a land on the spool. However, when a solenoid SSOL isenergized, the plunger 166 will be moved to the right against theurgency of spring 167, and. the line 168 will bev communicativelyconnected with the exhaust line 97, thereby bypassing the rate valve andpermitting the motor 125 to run at full speed. The present inventionincludes means for utilizing the shifting of the reversing valve 128 forinitiating the flow of coolant to the truing device so as to flood thediamond and the wheel with coolant during the truing operation. Thus,regardless of the stroke of the carriage as determined by the adjustmentof the dogs 67 and 68 (Fig. 6), coolant flow will always be initiated atthe beginning of the truing pass and will be terminated at the end ofthe pass. This feature eliminates the necessity of setting individualstops to control coolant flow in addition to the reversing dogs 67 and68. As shown in Fig. 2, the reversing valve 128 is provided with a pairof ports 1'70 and 171 which are connected by lines 172 and 173 with theactuating cylinder of a coolant control valve 174. When the spool 138 isin its centered position, as shown in Fig. 2, the ports and 171 are incom munication with ports 175 and 176 which are connected to the exhaustline 97 through a line 177 and a check valve 178. However, whenever thereversing valve is shifted in either direction, one of the ports 170 and171' will be connected to a pressure port 141 or 144 while the remainingport will be blocked off by lands formedon the ends of the spool 138.Hence, shifting of the reversing valve will cause pressure to be appliedto the chamber 179 of control valve 174 which lies beneath a plunger1800f the valve. This will cause the plunger. to be raised against theforce exerted by a. springlQL and permit a diaphragm 182 to be liftedoff a port 183 by the pressure of coolant flowing in through a line 184.The coolant will thereby be permitted to flow into an annular groove 185provided in the base of the valve and out through a line 186 to thetruing bar 36 (see also Fig. 3). It then passes through the spaceexisting between the interior wall of bar 36 and the exterior wall ofthe tube 116 to a coolant discharge pipe 187 mounted on the end of thetruing bar as shown in Fig. 2. When the valve 128 is again centered toterminate traversing movement of the diamond carriage, pressure will beremoved from the lines 172 and 173, and the spring 181 will cause thebottom of the plunger 180 to press against thediaphragm 182 and seal offthe port 183.

At the same time that pressure is delivered to the coolant valve 174, aportion of the fluid flowing through the line 172 is carried by a line183 to the coupling 115 (see also Fig. 3) to provide pressure foroperating the diamond turner 46.

The electrical control circuits for the automatic truing mechanism areshown in the wiring diagram (Fig. 7). Energy for the control circuit isprovided by a transformer 195 which energizes lines 196 and 197.Accordingly, when the Start push button is depressed in line 3 of thediagram, the relay LEA will be energized to start the electric motorwhich drives the hydraulic pump 120 (Fig. 2). At the same time thecontacts LEA in line 4 will be closed around the Start push button so asto lock in the relay and hold it energized after the push button isreleased. A pressure switch 1-PS, shown in line 5 of the diagram, isprovided for insuring that pressure lubricant is supplied to thegrinding wheel spindle before the grinding wheel motor may be started.Assuming this switch to be closed, line 198 will be now connected toline 196 so that depression of the Grinding Wheel Start push button inline 6 will energize a relay LED which, through suitable contacts notshown, energizes the grinding wheel motor. At the same time, a pair ofcontacts LED of this relay, shown in line 7, will be closed around thepush button to maintain the relay energized. The machine will now beconditioned for the commencement of an automatic truing cycle, theclosed contacts LED being effective to connect a line 199 with the nowenergized line198.

To start an automatic truing cycle, the Truing Start push button 19 inline 9 is depressed, thereby energizing the clutch coil 200 of thecounter 23 (Fig. 1), the coil being maintained energized by the contacts7CR (line 10) of a relay 7CR (line 24) which is energized by closure ofcontacts COB. The contacts COB are provided on the counter and remainclosed so long as the clutch coil 200 is energized.

As heretofore mentioned, the counter controls the number of passes ofthe diamond across the face of the grinding wheel. The counter per seforms no part of the present invention and may be any type of devicewhich is capable of being preset to count a predetermined number ofelectrical impulses and to provide a suitable signal when the count iscompleted. One form of counter which is especially suitable for thepresent purpose and which is commercially available is the reset type ofcounter manufactured by the Eagle Signal Corporation and known as ModelNo. HZ50A6. When the clutch coil of this counter is energized, thedevice is conditioned for counting, and each time a count coil 201 (line11) is energized and dcenergized, the mechanism of the counter will beadvanced one step until the desired count has been effected, whereuponthe contacts COB (line 24) will open upon the deenergization of coil201, thereby deenergizing relay 7CR and dropping out the clutch coil 200to terminate the counting operation and reset the counter for the nextoperation.

Assuming now that the carriage 30 is in its home position with the limitswitch 2LS operated by dog 67, the contacts 2LS in line 23 will therebybe held closed and relay 60R will be energized upon closure of contacts7CR in line 23. Hence, the normally open contacts 6CR in the line 12will be closed, and the count coil 201 will be energized so as tocondition the counter to count the first pass of the diamond across thewheels. At the same time, the normally open contacts of 6CR in line 13and 15 will also be closed, thereby causing relay 3CR to be energizedthrough the normally closed contacts 2TR (line 15) of timer relay 2TRand limit switch contacts 3L5 (line 13). It will be noted that relay 3CRwill be locked in around the contacts of relay 6CR in lines 13 and 15 bythe contacts 3CR in lines 14 and 16. The .contacts 3CR in line 26 willthus be closed, thereby energizing solenoid SSOL which will shift thespool 132 (Fig. 2) of pilot valve 129 to the left and operate thereversing valve 128 to cause the carriage to move away from homeposition and coolant to flow over the diamond.

As the carriage moves out of home position at the feed rate determinedby the setting of the rate valve 155, the limit switch ZLS will bereleased thereby deenergizing relay 6CR (line 23) and the count coil 201to enter the first count in the counter. At the same time, the contacts2L8 in line 25 will be closed, thereby energizing relay 8CR and causingthe contacts of this relay in line 32 to close. As the carriage moves tothe left, as viewed in Fig. 6, the rise on cam 73 will operate limitswitch SLS after the doamond has finished truing the wheel 12. This willcause the contacts of this limit switch in line 32 to close, therebyenergizing SSOL and operating the rapid traverse valve 165 (Fig. 2) tobypass the rate valve and cause rapid traverse of the carriage. Rapidmovement of the carriage will continue until the roll of limit switch5LS leaves the high portion of the cam as the diamond approaches thewheel. The limit switch will thereupon be released and SSOL deenergizcdto reintroduce the rate valve into the circuit and reduce the rate oftravel of the carriage to a normal feed rate.

When the reversing dog 68 strikes the contact roll 72 of limit switch3LS, the contacts of this limit switch in line 22 will be closed,thereby energizing relay 5CR. This will cause the normally open contactsof this relay in line 11 to close, thereby again energizing the countcoil 201 and preparing the counter for the next count. Also, thecontacts 3LS in line 13 will open, thereby deenergizing 3CR. This willopen the contacts 3CR in lines 16 and 26 so as to drop out timer relay3TR and deenergize solenoid 3SOL. When relay 3TR is dropped out,solenoid 6SOL will be energized by the instantaneous closing of contacts3TR-2 of the relay in line 33 and the timed opening of the delaycontacts 3TR-3 also in this line. The solenoid 6SOL will thereby bemaintained energized from the time relay 3TR is deenergized until thedelay contacts 3TR-3 time open. The valve spool 93 (Fig. 5) will therebybe operated to move the piston and advance the diamond by the amountdetermined by the setting of the selector knob.

The timer relay 3TR has a second pair of delay con tacts shown in line20 which will time closed when the relay is deenergized. When thesecontacts close, relay 4CR will be energized, the contacts SCR in line 19and 8CR in line 13 being closed at this time. Relay 4CR will be lockedin around the SCR and 3TR contacts by the contacts 4CR in line 21.Energization of relay 4CR will reenergize relay 3TR by closing contacts4CR in line 17.

After the contacts 3TR in line 20 have timed closed to energize relay4CR, the contacts 4CR in line 30 will close and energize solenoid 4SOLto move the slide away from the reversal position and toward the homeposition with flow of coolant to the diamond. As the slide leaves thereversal point, the dog 68 will release limit switch 3L8, therebyopening the contacts 3LS in line 22 to deenergize relay SCR and completethe second count. At the same time, the contacts 3LS in line 13 willclose to energize timer relay 2TR.

After the wheel 11 has been trued (Fig. 6), the cam 73 will operatelimit switch L8 to cause rapid traverse of the diamond to the secondwheel 12.- The wheel 12 will then be trued at a normal feed rate afterwhich limit switch 2LS will be operated by the dog 67. This will openthe contacts 2LS in line 25 and close thecontacts 2LS in line 23,thereby deenergizing relay 8CR and energizing relay 6CR to energizeco'il 201 and condition the counter for the third count. When relay 8CRis deenergized, relays ZTR, 3TR and 4CR will drop out, therebypermitting contacts 2TR in line 15 to time closed and contact 3TR-3 inline 33 to time open. Since the contacts 3TR-2 are now closed, thesolenoid 6SOL will be energized to provide diamond advance. As soon asthe contacts 2TR (line 15) time closed, the relay 3CR will be energizedsince the contacts 6CR in lines 13 and 15 are now closed. The relay 3TRwill now be energized to deenergize solenoid 6SOL and to open itscontacts in line 20. When the relay 3CR is energized, its contacts inline 26 will be closed, thereby energizing solenoid 3SOL to move theslide away from home position for the next pass and turning on thecoolant.

It will be noted that if the counter counts out in the home position ofthe carriage, the contacts COB will open to deenergize relays 7CR and6CR. This will occur, however, after relay 3CR is energized to lockitself in aro'und the contacts of relay 6CR. Therefore, the carriagewill move away from home position and continue to the reversal position.At this position relay 30R will drop out but the contacts 7CR in line 18will be closed so that timer relay STR will not drop out to therebyenergize solenoid 6SOL so that no advance of the diamond will takeplace. Hence, the last pass from the reversal point to the home positionwill be a dead pass. Since the first step of the counter takes place inthe home position at the beginning of the truing operation, an odd countset up on the counter will cause the last pass to be a dead one while aneven count, i.e., when the counter counts out with the slide in thereversal position will cause the last pass to be a cut pass. Thus, theoperator can select at will either type of operation by setting up onthe counter either an odd or an even count.

When the carriage arrives in home position after the counter has countedout, the relay 6CR will not be energized due to the open contacts 7CR inline 23, and relay 3CR will not be energized. Therefore, the carriagewill stop in home position, and the truing cycle will be concluded.

A manual truing operation may be performed by manipulation of theAuto-Manual selector knob 108 (Fig. 5) which operates limit switch 4LS.In this case, the contacts 4LS in line 13' (Fig. 7) will be open,thereby deenergizing the automatic truing control circuit. With a manualsetting of the knob 108, the carriage may be moved away from home bymoving the switch 202 (line 28) to the Out position. This will causesolenoid 3SOL to be energized since the contacts 4LS in line 28 are nowclosed. If it is desired to move the carriage to'ward home position, theselector switch 202 is turned to the In position whereby solenoid 4SOLwill be energized. Rapid traverse of the cross slide may be selected inmanual operation by depression of the puth button switch 203 (line 31)which energizes solenoid SSOL, thereby bypassing "the rate valve andpermitting the hydraulic motor 125 (Fig. 2) to run at full speed.

The manual control provided by the Auto-Manual selector knob 108 isuseful in setting up a job and preparing the machine for a fullyautomatic truing operation. With the knob 108 set to Manual position,the diamond may be backed away from the grinding wheels by manipulationof the hand wheel 53. The selector switch 202 (Fig. 7) is then turned tothe Out position to move the carriage away from home position. The ratevalve 155 (Fig. 2) is now adjusted to provide the desired feed rate ofthe carriage for truing of the wheels. After the diamond has cleared thesecond wheel, the carriage is 10 stopped by turning switch 202 to theStop position, and the dog 68 is then adjusted to a point where it justoper ates the roll 72 of limit switch 3L8. The switch 202is now turnedto the In position to return the carriage-to home position. The carriageis stopped in home position truing pass. The Auto-Manual selectorknob'108 is no'w turned to the Auto position, and the truing mechanismis now ready for an automatic cycle which may be initiated by depressingthe Turing Start push button shown in line 9 of Fig. 7. I g t Havingthus described the invention in connection with one possible form orembodiment thereof and having used, therefore, certain specific termsand language therein, it is to be understood that the present disclosureis illustrative rather than restrictive and that changes andmodifications may be resorted to without departing from the spirit ofthe invention or the scope of the claims which follow.

I claim:

1. In a grinding machine having a base, a grinding wheel supported onsaid base, and a source of power for driving said wheel, the combinationof a carriage mounted on said base for movement thereon in a directionparallel to the axis of rotation of said wheel, a slide supported onsaid carriage for movement at right angles to the direction of movementof said carriage, a wheel truing unit supported on said slide formovement toward the peripheral face of said grinding wheel, means forautomatically traversing said carriage back and forth on said basebetween a home position and a reversal position, means for advancing thetruing bar by a predetermined amount each time the carriage arrives atthe home position and the reversal position, means for counting apredetermined number of passes of the truing bar across the peripheralface of said wheel, and means controlled by said counting means forpreventing the automatic ad vance of the truing bar in the next reversalposition of the carriage when said counting means has counted out in thepreceding home position thereof.

2. In a grinding machine having a base, a grinding wheel supported onsaid base and a source of power for driving said wheel, the combinationof a carriage mounted on said base for movement thereon in a directionparallel to the axis of said wheel, 'a wheel truing unit mounted on saidcarriage, a hydraulic motor for driving said carriage, a reversing valvefor controlling the operation of said motor, and means controlled bysaid reversing valve for causing coolant to be delivered to the grindingwheel during each, traversal of the truing unit across the face of saidwheel.

3. The grinding machine of claim 2 wherein said lastnamed means includesa coolant control valve, and means operatively connected with saidreversing valve for operating said coolant control valve.

4. In a grinding machine having a base, a grinding wheel supported onsaid base and a source of power for driving said wheel, the combinationo'f a carriage mounted on said base for movement thereon in a directionparallel to the axis of rotation of said wheel, a wheel truing unit onsaid carriage, means for automatically traversing said carriage and saidunit back and forth on said base between a home positio'n and a reversalposition, said traversing means including a hydraulic motor for movingthe carriage, a reversing valve for controlling the operation of saidmotor, and means moving with said carriage for initiating the reversalof said valve when the carriage moves into its home position and intoits reversal position, and means controlled by said reversing valve for11 causing coolant to be delivered to the grinding wheel during eachtraversal of the truing unit across the face of said wheel.

5. The grinding machine of claim 4 wherein said lastnamed means includesa coolant control valve, and means for causing said co'olant controlvalve to be operated to deliver coolant to the grinding wheel upon eachreversal of said reversing valve.

6. In a grinding machine having a base, a grinding wheel supported onsaid base and a source of power for driving said wheel, the combinationof a carriage mounted on said base for movement thereof in a directionparallel to the axis of rotation of said wheel, a slide supported onsaid carriage for movement at right angles to the direction of movementof said carriage, a wheel truing unit supported on said slide formovement toward the peripheral face of said grinding wheel, means forautomatically traversing said carriage back and forth on said basebetween a home position and a reversal position, and means for advancingthe truing unit by a predetermined amount each time the carriage arrivesat the home position and at the reversal position, said advancing meansincluding a solenoid, an energizing circuit for said solenoid, and atimer relay having a pair of instantaneous contacts and a pair of timedelay contacts connected in series with said solenoid across saidenergizing circuit for first energizing said solenoid and thendcenergizing said solenoid after a suitable time delay.

7. The grinding machine of claim 6 including means for counting apredetermined number of passes of the truing unit across the peripheralface of said grinding wheel, and means controlled by said counting meansfor preventing the energization of said solenoid in a reversal positionof said carriage after said counting means has counted out in apreceding home position thereo'f.

References Cited in the file of this patent UNITED STATES PATENTS1,976,123 Haas Oct. 9, 1934 1,976,124 Haas Oct. 9, 1934 2,522,485 SilvenSept. 12, 1950 2,759,304 Silven et al. Aug. 21, 1956

